Sewage treatment



June 19, 1945.

` A. C. DURDIN, 3D SEWAGE TREATMENT Filed Aug. 5, 194D Patented June 19, 1945 UNITED STATES PATENT OFFICE 2,378,756 sEwAGE TREATMENT Augustus G. Dllrdln, III, Niles Center, Ill. Appuwion August s, 1am.` serial Nu. 350,214

' 4 clams. (ci. 21o-s) and apparatus for treating-sewage.

One of the objects of the present invention aerobic sludge obtained froma. se tank prior to the settling of that sludge to the' bottom of the tank.

A tux-ther object of the present invention i6 resides in the provision of a new and improved method for classifying the sludge in the settling tank, whereby highly virile and aerobicA sludge is uniformly and effectively separated from the heavier and non-aerobic sludge.

20 A further and somewhat broader object of the invention is the new and im- A further object in the provision of apparatus for carrying out the methods described above.

A further object of the present invention is in the provision oi a ing to the principles outlined above with means whereby the separated materials may be readily and uniformly separated.

A further object of the present invention is in slderation is the highly virile and aerobic sludge, so that itmaybereadilysupplied lmrmiirture with the raw Sewage.

45 A further object of the present invention is to provide a classiner of the type above, with means for disposing of any scum that is likely to form therein.

,sides in the provision .the present invention,

30 of the present invention is classifier operating ccord- 35 o circular and is preferably the methods of the present invention, which includes a settling tank embodying other features of the invention.

The sewage treatment apparatus illustrated in the iigure consists oi'. in the main,4 a settling tank lli, centrally of which is located the classier l2 forming one of the important features of the present invention, an aeration tank I4 connected by a conduit I6 to the classier and supplied with raw sewage through a. commuter i8 and, in accordance with another feature of with highly virile and aerobic sludge from the classifier through conduit 20 and, ilnally, of a sludge digestion tank 22. The latter is connected by conduit 23 to a sump 24 formed centrally and at the lowermost portion of the settling tank. To avoid the use of a pump for forcing sewage from the aeration tank to the settling tank, .the level of sewage in the aeration tank may be maintained about six or eight inches above the liquid level in the settling tank. 4

The settling tank i0 may take any desired shape and has been illustrated, for example, as

i provided with concrete'side walls 26 and a sloping toward the sump 2l. An annular clear purpose of carrying oiI clear nltered liquid. The launder 3d is denned by an upstanding outer wall 34 iormin gb part oi' the main concrete side walls and a annular inner weir or overiiow baille 36 comprising a metal plate suitablvr secured to an angle iron fastened to a. portion I8 the launder 30.

The lower portion of the settling tank I0 constitutes a sedimentation zone. The sludge collecting at the bottom is scraped toward the sump by a scraper consisting of a frame l upon which is mounted a plurality of scrapers 42 for scraping the sediment or sludge at the bottom oi the tank into the sump 24. and a centrally disposed scraper 44 extending into the sump, the purpose of which is to assist in the discharge of the sludge into the digestion tank through the pipe 2l.

The sludge scraper is supported on a central upright shaft 4B rotated by suitable drive means such, for example, as an electricl motor 48. The scraper and its driving mechanism are supported on a pair ofI-beams 50 (only one of which is shown in the ligure) extending across and supported by the annular tank wall 34.

The settling tank includes ltering means $2 which may be a cloth or wire screen having an annular shape and located near the inner periphery of the settling tank and below the normal water level in the latter, so that the liquid ilowing into the launder passes therethrough in an upward direction. The ltering means is cleaned by forcing clear liquid collected at a point above the ltering means downwardly throughV the screen by cleaning apparatus including a liquid pump 5I, a pump motor Si, and a back-wash pressure chamber 58 directly above the filtering means.

The above described type of iilter and filter cleaning means. broadly considered, does not constitute any part of the present invention, although the present invention does include improvements in the construction and arrangement of the cleaning apparatus, which improvements will be described shortly. The above described type of nltering and cleaning means is disclosed in Patent No. 2,065,836, granted on December 29, 1936, to Paul A. Thayer. V

The ltering means is, as has already been indicated, located below the normal liquid level in the settling tank, which level is determined by the top of the weir 36. This normal level is indicated by a line denoted by reference character 60. The illtering means is preferably supported on a pair 'of spaced-apart annular angle irons B2 and 84, the former of which is supported by a number of angularly disposed brackets 66 and the latter upon the concrete side walls 26. The

annular angle iron supports 62 and 8l have mounted thereon annular angle iron tracks 68 and 1n, respectively, for a purpose which will appear shortly. V

The cleaning apparatus is mounted for rotation around the tank so that only a limited portion of the filtering means is cleaned at any one time. The construction of the cleaning apparatus is simplified considerably by mounting the pump 54 below the liquid level and the motor 56 above the liquid level. These two elements of the cleaning apparatus are supported in this manner upon a base plate 'I2 supported. in turn, upon a pair of spaced-apart, generally radially disposed arms I4 (only one of which is illustrated) mounted for rotation around the tank. The outer ends of the supports 'Il are secured in suitable manner to a pair of wheels 'I'B (only.

one of which is shown) and the inner side of the supports are most conveniently secured to three equidistantly spaced-apart wheels 18 (only two of which are shown). The two sets of wheels 16 and 18 are mounted for rotation upon outer and inner tracks B0 and B2, respectively. Track B0 is suitably supported above the liquid level by `a number of spaced-apart supporting plates 8l secured to portion 3B of the tank wall, and track 82 ls similarly mounted above the upper end oi the centrally disposed classifier i2 heretofore referred to. The cleaning apparatus is propelled around the settling tank by a motor 88 suitably coupled through gear reduction apparatus to one of the wheels I5 and mounted upon the base plate 12.

According to another of the features of this invention the back-wash pressure `chamber 58 is mounted directly above the iiltering means 52 and is connected in articulated manner to the cleaning apparatus propelling mechanism. The chamber is provided with a plurality of spacedapart rollers engaging the previously mentioned tracks BB and 10. so that it is at all times maintained in close contact with the filtering means, irrespective of variations in level and lateral displacement between the propelling mechanism and nltering means. The articulated connection between the back-wash pressure chamber and propelling mechanism is provided by a pair o! hanger arms $0, each ot which comprises a pair of swiveled connections and a pair of telescopically arranged tubes 92. Liquid is supplied to the back-wash pressure chamber through a pipe il connected to the' pump discharge, as by a flexible hose connection (not shown), whereby the position ot the chamber to the lterlng means is not affected by the location of either the propelling mechanism or pump.

One of the primary features of the present in vention resides in the'provision oi a new and improved method oi activated sludge sewage treatment which consists in treating (i. e. "seeding") the raw sewage with Valhighly virile and aerobic sludge. This sludge is obtained trom the settling tank prior to the time it settles and is separated from the heavier, non-aerobic and less virile sludge settling to the bottom of the tank and which has heretofore been used in such treatment of the raw sewage.

The supply of this highly virile and aerobic sludge is 'obtained by means of the classier' I2 which operates and is constructed upon entirely new principles to insure an eiective and uniform separation of the aerobic from the non-aerobic sludge. I

The classiiier consists of a generally cylindrical shell 8B suspended in suitable manner from the beams 50 and extending into the tank a distance somewhat less than half the depth of the liquid. Sewage from the aeration tank is injected tangentially into the classier through an opening IIB located approximately midway between the bottom of the shell Q6 and the liquid level. When the liquid is thus injected at a velocity. dependent mainly upon the characteristics of the sludge and proportions of the classiiier and sewage conduit, the sewage flows around the tank and the heavierand less aerobic sludge gathers in the center of the classier and. falls through the open lower end'thereof to the bottom of the tank while the lighter. highly virile and aerobic sludge gathers nearer the inner wall of the classifier.

The lighter, highly virile and aerobic sludge is prevented trom falling to the bottom of the settling tank and is utilized to seed the sewage supplied f't-.he aeration tank, as previously mentioned. This lighter sludge is prevented from falling tothe bottom by an annular upwardly inclined and centrally extending bale IM suitably secured to the lower end of a second cylin- "f mstance a; -consti ma for the .drlal shellA ilpncenirie to @aanwending-somein. l e ,so vrtlliaj'tf; the light' .s llicigegradually to tli'ehopper news 1pm-fiamma, r. l'H-i @Waffle-washable@- aith 'e bottom mstarce. anjalrl 'lift may bensedin which event eight) openings "fit1 ieiiaihgnom the interior of openings arehpi-frablyf have their low''runds atlthe 'f that the 'scun'i"vvlllllnivl l tion of the tank located liquid llvelf so thereover into' the 'porbetv'v'een the` hopper and filtering means-.The' openings` ilfar'efpreerf ably located in staggered relation to the slots |08 inshell |02.

'Ihe heaviest part of the sludge flowing past deilector plate falls directly to the central part of the bottom of the settling tank and the lighter parts at points therebetween and the tank wall. All but the lightest parts of this sludge are prevented from reaching the ltering means baille structure com- 2 and H4 supported means support 68.

Scum forming at the top of the liquid between the baille structure and hopper, or iowing into region from the upper part of the elassier is collected in a rectangular hopper IIE having a bottom inclined downwardly and outwardly whence it is discharged into the digester tank 22 through conduits ||8 and 23. The scum is carried into the hopper by a scrapper blade hingedly supported from one of the propelling mechanism supportsI 14. The scum is elfectively prevented from collecting at the sides of the hopper by a pair of aprons |22 (only one of which is shown) extending outwardly and downwardly from the sides of the hopper. The aprons are made sumciently wide to prevent the scum from getting caught underneath them.

To prevent damage to the equipment and to minimize impairment of the treating process as a result of accidental excessive supply of sewage, there is provided an overow system that discharges into the clear liquid launder 30. 'This system comprises an annular passageway dened by the baille plate i i2 and an annular plate |24,

the settling level obtaining 10 v fromme comminutor is is and' highly' active 'portion is forced .the Vupper end of whichdetermines the overow level. |24 is concentric to and of lesser .excessive supply of sewage is supplied to tank, the liquid level in the portion :wenken clog V.rupt proper-"operation of the apparatus. Inoperation of the apparatus the raw sewage l i mixed with the highly virile light sludge 'obtaine from the settling tank 'and the inixture supplied tothe aeration tank. VFrom theaeration tank the sewage flows by grav- 'to the classine'r I2 through conduit Iii.` The dischaged tangentlally into the classisewage to the Outside,

' whilev the j'heavierand less active portions gather st thecenter.

'the bottom bf the tank I'he highlyactive portion is caused by defleciiow in the passageway detned jlfayfsliells 86 and.x |02, w ence it flows into hopper through weirs |06. The sludge'collected in @amaca me, the' raw sewage.' The use ,of the highly active light -sludge 'provides a very eiective method of sew- "age-treatmritas this sludge is more effective upon theraw sewage than sludge collected from The heavier sludge either [gils directly to the bottom of the tank or settles t erein as the liquid flows to the launder through the filtering means.

then discharged into the digestion tank.

'I'he llltering means is cleaned, as already described. by forcing clear filtered liquid down wardly therethrough by means of the pump. A very eiective and uniform cleaning is obtained by mounting the pressure chamber 5B directly over the ltering means and supporting it on a track independently of the propelling mechanism. The mounting of the pump below the liquid level results in shortening the pump conduit connections and more eflcient operation of the pump.

The scum formed in the classier flows into the center region of the tank where lt is gathered with the scum formed in that region and deposited in the scum hopper. From the hopper the scum is discharged into the digestion tank.

Overowing of the-sewage into the tlltering means and the building of excessive pressures against the filtering means is prevented by the overflow system discharging into the launder through conduit |28.

Although this invention has been described in considerable detail, it is to be understood that the description is intended to be illustrative and not limiting in nature. as the invention may be cluding in combination, a generally cylindrical and generally vertically disposed open bottom chamber. means for injecting liquid into said chamber tangentialiy to the side walls thereof and effecting slow downward movement oi the liquid in` the chamber, thereby to gather the heavy and lig-ht'materials in central and outer zones of the' chamber. a'nd means for causing the liquid in said zones to' follow separate paths thereby to eiect separation of the materials. said last mentioned means including an annular passageway concentric to and surrounding the chamber and a centrally open annular inwardly and upwardly extending deilector the lower portion oi which is located below Athe lower end of the chamber to provide communication between the annular passageway and chamber.

2. A classliler for sludge supplied to a settling tank. including in combination, a generally cylindrical and generally vertically disposed open bottom baille located centrally of the tank and extending from above the normal liquid level in the ta'nk a considerable distance below the liquid level, means located between the liquid level and bottom of the baille for injecting liquid inside said bailleV tangentially to the side walls thereof, thereby to gather the heavy and light materials in central and outer concentric zones within the baille, a cylindrical plate concentric to and spaced outwardly from the baille to denne an annular passageway, a centrally open deilector securedA to said plate below the baille and extending upwardly and toward the central zone within the baille for effecting separation of the liquids ln the two zones, whereby the liquid ln the central zone ilows into the settling tank and the liquid in the outer zone ilows into said annular passageway, means associated with said passageway for collecting the iight sludge. said last mentioned means including a hopper surrounding said cylindrical plate and communicating with said annular passageway by means of slots at the upper end of said plate extending downwardly approximately to the normal liquid level in the tank, and sludge outlet means associated with said hopper.

3. A classifier according to claim 2, wherein passageways extending romcwithin the baille to the exterior oi the hopper and located immediately above the normal liquid level in the tank are provided for the purpose of disposing of scum `qiilecting within the baille.

4. In a settling tank ci the type having a peripheral launder and a peripheral filter through which clariiled liquid flows upwardly into the launder. a tubular baille into which material to be settled is discharged, and a second baille extending irom above to below the top oi the launder adiacentthe inner side oi the filter. an overflow device including in combination, means including generally a cylindrical and vertically extending wall located inwardly oi the second baifle and extending downwardly a,from above t0 below the tcp of the launder inthe tank and having an overow outlet above the top of the launder out below the top of the second baille, means for closing the space between the lower portion of the wall and the second baille, thereby to constitute an overllow chamber' located inwardly of the second baille and communicating with the interior of the tank inwardly oi and below the top of the second bame .and above the top of the launder within the tank, and conduit means below the top of the launder in the tank for connectlng said chamber to the launder and conducting overilow to the launder.

AUGUSTUS C. DURDIN, III. 

